Inferior surgical outcomes following reverse total shoulder arthroplasty for nonunion and malunion compared to acute arthroplasty: a nationwide matched cohort analysis

Reverse total shoulder arthroplasty (rTSA) has become popularized in the management of acute proximal humerus fractures (PHF). Limited evidence exists to compare the outcomes of acute rTSA to management following failed open reduction and internal fixation (ORIF). We aimed to analyze the differences between acute rTSA for PHF compared to subsequent rTSA for nonunion/malunion. Patients who underwent primary reverse total shoulder arthroplasty (rTSA) from 2016-2020 were identified in the Premier Healthcare Database (PHD). Nonunion, malunion and hardware complication patients were identified using ICD-10 diagnosis codes and compared to acute PHF controls. Patients were matched in a 1:1 fashion to acute fracture based on age (+/- 3 years), sex, race, and presence of pertinent comorbidities. Patient demographics, hospital factors, patient comorbidities and 90-day complications were assessed and compared between the two cohorts. Descriptive statistics and regression analysis were employed with significance set at p<0.05. Prior to matching, 8,561 nonunion/malunion cases and 11,134 acute rTSA controls were identified. Patients undergoing acute rTSA for PHF were older, had longer length of stay and higher total costs (p<0.0001). When compared to acute rTSA for fracture, nonunion/malunion patients were at increased risk of multiple surgical complications including periprosthetic joint infection (OR 4.56, 95%-CI 2.95-7.04, p<0.0001), periprosthetic fracture (OR 2.86, 95%-CI 2.09-3.93), stiffness (OR 2.01, 95%-CI 1.17-3.44, p=0.01), and dislocation (OR 2.37, 95%-CI 1.80-3.12, p<0.0001). However, patients undergoing acute rTSA had higher rates of all medical complications investigated, including DVT, PE, pneumonia, MI, AKI and sepsis (p<0.001). Reverse total shoulder arthroplasty after nonunion/malunion of proximal humerus fractures is associated with increased risk of surgical complications compared to acute rTSA. Initial rTSA for proximal humerus fractures may mitigate subsequent increased risk of surgical complication and should be considered as the initial treatment option in patients with proximal humerus fractures. However, the increased risk of medical complications seen in acute PHF warrants attention and diligent medical optimization from providers. Level III; Retrospective Case Control Study